Out of curiosity, did you happen to read Kurzweil's recent book on HHMMs?
I think the safest answer is that a HMM is just a specific way of mathematically writing down an updating Bayesian network.
No, never heard of it. I'm not an Utopian, and from what I know about Kurzweil's ideas and arguments, they don't seem to be sound enough.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.